> Is it too late to ask for styles to be exported/injected
> into the pdf as a key, or can this already be done ?

Styles are written as layers in the PDF - if you open the layer pane in Adobe Reader you will see them listed there and they can be hidden or shown individually (see pics below). Outlines by default go on their own separate individual layer rather than using the style layer, but you can change that by clicking "Line style options" on the PDF export options dialog.